AVS 46th International Symposium
    Surface Science Division Wednesday Sessions
       Session SS-WeP

Paper SS-WeP31
CV, XPS, SIMS and ISS Examination of Zirconium Passive Film Breakdown in the Presence of Sulfate

Wednesday, October 27, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: R Schennach, Lamar University &Texas A&M University
Authors: R Schennach, Lamar University &Texas A&M University
A. Mamun, Lamar University
N. Kunamneni, Lamar University
D.L. Cocke, Lamar University
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Passive films on zirconia have been prepared by potentiodynamic polarization in the presence of a range of anions and at various pH values. Sulfate has been found to produce unique transpassive peaks that appear to be associated with an amorphous to cyrat alline transitionand subsequent enhanced species transport along the resulting grain boundaries. The passive film breakdown can be qualitatively described by E@sub np@ = E@sub c@ + @eta@ + @PHI@ +E@sub inh@. Where E@sub np@ is the pitting potential, E@sub c@ the corrosion potential in acidified solution, @eta@ the polarization necessary to obtain a current density high enough to maintain acidity inside the pit, @PHI@ the potential drop inside of the pit and E@sub inh@ the contribution to pitting potent ial resulting from inhibitors present. XPS, SIMS and ISS have been used to characterize the films before and after the passive film breakdown. The results of these surface studies along with the variation in CV scans have been used to describe the process and to present a model that involves either IR drop and/or local acidification. The involvement of chemically bound water oxidation and local oxygen evolution are presented as well.